Field of the Invention
An embodiment of the invention relates to the field of DSL (Digital Subscriber Line) communications, and in particular, a management system to enhance performance, for example, by reducing noise interference, in a DSL network.
Description of Related Art
The world market for DSL services presently exceeds 300 million lines, and continues to grow. Many of the DSL lines in operation today are limited in the rate of their transmission by the noise levels received by the customer's modem. The sources of such noise are numerous; they enter the DSL line either within the operator's plant or within the customer's home, and may either be stationary, intermittent, or impulsive in nature. Typical sources of noise are combinations of such common sources as DSL crosstalk, AM radio signals, television set interference, lighting, washing machines, alarm systems, and other appliances. The characteristics of noise on a given line may change over time as various noise sources are energized or disabled or with the level of energization or characteristics of the propagation path between the source and the line, such as in the variation with time of AM radio broadcast power levels.
In some cases, received noise on the line impairs not only the rate of data transmission, but the quality of the service (QoS) as perceived by the customer. This distinction has become more important as the services delivered over DSL have changed in recent years. While DSL has traditionally been used for transmission of best-effort packet data (email, Internet, instant messaging), which is relatively insensitive to transient packet errors, new applications transported over DSL such as IPTV may be highly sensitive to transient degradations caused by e.g. impulsive noise.
In current practice, DSL line noise is generally dealt with by reducing data rate, which makes the DSL service less sensitive to noise, and not by actively removing or canceling noise on the DSL line. In the present art there are certain devices that attempt to cancel specific types of noise on a DSL line. These embodiments are limited in that they attempt to cancel noise independently; they cannot be centrally managed, do not make use of external information (such as diagnostic information on the line, historical line noise environment and performance, configuration of the telephone cabling), and are not configurable to reflect users' performance preferences. Improved practice may also involve a significant computational capability that would not be practical or cost-effective to locate in every DSL customer's cancellation apparatus. Such complexity could become cost effective if shared over many customers by a central control system. Further, a central computational device would enjoy the benefit of statistical knowledge collected from other DSL connections and cancellations that would benefit the level of improvement on the line presently under direct assistance.
A system or device that can improve DSL network performance through the control and management of DSL line noise across the entire network using a centralized command interface to manage equipment at the subscribers' premises represents a novel technical advance over present art. The technical advance is relevant to practice because DSL operational issues such as capital costs, operating costs, and services that can be practically offered to customers are driven significantly by the performance of the physical-layer DSL devices. This performance, in turn, depends strongly on DSL line noise.